BIG PC Games Problem

Counter Strike will sometimes load and work for a while but then it loads and freezes or just crashes out of the blue. I use Garry's Mod alot aswell but that usually freezes while loading aswell. I also have GTA 3 and that worked up up until now. All it does is when I click the icon to start it, the little hourglass appears next to the cursor for like a second then nothing happens. None of my games work properly now. It is really weird because before all of them worked totally great, with absolutely no lag at all. I have the latest video card drivers. This happened to me on another user so I made a new one(it had a really cluttered desktop anyways) and then the games all worked. Now they're screwing up again and I have no idea what's happening. PLEASE HELP!

I shut off pretty much everything, including my firewall(which also is not Norton).

Before it would run all my games and would run absolutely perfect. I could minimize the game and it wouldn't really have an effect.
It couldn't be anything I recently did to my computer because this has happened to my twice.

Here are my specs.

I have an ATI RADEON XPRESS 200 series video card with the drivers up to date(95% sure).

For GTA3, go to your "My Documents" folder, zip the "GTA3 User Files" folder for backup purposed & then delete the folder. Try running GTA3 again & see if it works (it did for me when GTA3 stopped working for no apparent reason).

Damn, it was so close. I tried deleting the save files and when I started GTA 3, the screen went black for like 3 seconds then went back. Before I deleted the files nothing would happen exept an hourglass would appear right next to the cursor and now the screen goes black for a couple seconds. That made a difference but I don't know what to do now!

EDIT: It works now. I just put the reolution all the way down to the worst. Seems like it had trouble setting the right resolution, that's why it would go back tot the screen instead of starting. Thanks everybody!